5 July 2013. Attention-deficit hyperactivity disorder (ADHD) and schizophrenia share genetic roots, according to two studies published May 23 in the British Journal of Psychiatry. Despite the fact that the two disorders emerge at different times—ADHD emerges in children, making it hard for them to concentrate, while schizophrenia announces itself in early adulthood—some genes contribute to the development of both disorders, the studies find.

One study, led by Henrik Larsson of the Karolinska Institute, found that first-degree relatives of people diagnosed with ADHD—parents, siblings, or children, who share about half their genetic code—were about twice as likely to have schizophrenia or bipolar disorder as relatives of people without psychiatric disease. This suggests that vulnerability to both disorders is inherited within families. The second study, led by Nick Craddock of Cardiff University, U.K., looked at the DNA of children with ADHD and found it shared some characteristics with the genetic code of people diagnosed with schizophrenia.

The results support previous hints of an association between the two disorders, though they do not mean that children with ADHD are destined to develop schizophrenia. Instead they may help scientists discover molecules and brain circuits that lead to both disorders. (For more details on this study, see SRF related news story.)—Michele Solis.